Read it through once

The coating itself varies from "bright yellow, pale ochre, citron, chestnut colour, to mouse colour, different shades of grey and green, cream colour, lead colour, blue-black or pure black, tawny, brown, rusty red or pure white." The cups of one kind (_Lecidea_[77]) are black, whilst those of _Lecanora_ are generally reddish-brown. But they may be a ghostly pale hue which stands out plainly against the grey-green background of the frond.